JP5178275B2 - Lubricating oil composition - Google Patents

Description

  The present invention relates to a lubricating oil composition. Specifically, the present invention relates to a lubricating oil composition having excellent oxidation stability.

  Lubricating oils are made by blending additives according to their use using mineral oil or chemically synthesized oil as a base oil. In particular, the selection of the base oil and the antioxidant is the most important factor for using the lubricating oil for a long time. In general, mineral oil-based lubricating oils are used to refine petroleum hydrolyzed oil fractions by solvent refining, hydrocracking, solvent dewaxing, sulfuric acid washing, clay treatment, etc., as well as advanced hydrorefining, aromatic content, sulfur Lubricating oil compositions having high oxidation stability are manufactured by blending various antioxidants with this highly refined base oil while reducing the content and basic nitrogen content to an extreme.

In recent years, in lubricating oils used in equipment where importance is placed on oxidation stability at high temperatures, such as turbine oil, compressor oil, or hydraulic hydraulic oil, which are associated with higher output, smaller size, and longer life of equipment in recent years. High oxidation stability and sludge generation prevention ability tend to be required.
Highly refined base oil that is highly hydrorefined has very few aromatic compounds, sulfur-containing compounds, nitrogen-containing compounds, oxygen-containing compounds, etc. that cause sludge generation, and few components that interfere with the action of antioxidants. For this reason, it has been inevitable to use it as a base oil for lubricating oils used in equipment that requires high oxidation stability in recent years.

  Since highly refined base oil has a low aromatic content, there are problems such as low solubility of a highly polar compounding agent and adverse effects on rubber seal materials, and there are technical problems. Moreover, since the generated sludge has low solubility, there may be a problem of accumulation and a problem of clogging of the filter. For this reason, various antioxidants and their blending techniques have been developed (see, for example, Patent Documents 1 to 6).

On the other hand, solvent refined base oils that are low in refining costs and inexpensive because they do not undergo advanced hydrorefining have a high content of aromatics and sulfur, and therefore have superior properties not found in highly refined base oils. ing. For example, sulfur compounds present in base oils are known to act as natural antioxidants. In addition, a highly polar compounding agent has high solubility, and more can be added. In addition, there is an advantage such as high solubility of sludge. However, in order to use this inexpensive solvent-refined base oil, it is indispensable to select and blend antioxidants that are less susceptible to the effects of aromatics, sulfur and other impurities.
JP 63-223094 A JP-A-2-284994 Japanese Patent Laid-Open No. 3-20394 JP 2000-129281 A JP 2003-27081 A Japanese Patent Application Laid-Open No. 2004-262979

In order to perform a high-level refining treatment on the lubricating base oil, a large-scale apparatus, a large amount of hydrogen, and a large amount of energy are required, and the highly refined base oil has an economical disadvantage. Therefore, development of a lubricating oil composition having high oxidation stability and long life using inexpensive solvent refined oil as a base oil is desired.
An object of the present invention is to provide a lubricating oil composition that has excellent antioxidant performance even when a solvent-purified base oil is used, and that does not deteriorate oxidation stability even when used for a long time under high temperature conditions. And

  As a result of diligent research on the above problems, the present inventor has sufficient oxidation stability by simultaneously blending a specific triazole derivative and an alkylphenoxycarboxylic acid in addition to an antioxidant into a solvent-purified base oil having a low refining cost. The inventors have found that a lubricating oil composition can be obtained and have completed the present invention.

  That is, the present invention has (A) a composition having a total aromatic content of 10 to 50% by mass, a sulfur content of 0.1 to 1.0% by mass, a viscosity index of 85 to 100, Mineral oil having a point of −10 ° C. or lower is used as the main component of the base oil, and based on the total amount of the composition, (B) an antioxidant is 0.01 to 5% by mass, and (C) is represented by the following general formula (1). The present invention relates to a lubricating oil composition comprising 0.01 to 0.1% by mass of an alkylphenoxycarboxylic acid and 0.005 to 0.1% by mass of (D) a triazole derivative.

（式（１）中、Ｒ^１は炭素数１〜１２のアルキル基、ｎは１〜６の整数を示す。）

(In formula (1), R ¹ represents an alkyl group having 1 to 12 carbon atoms, and n represents an integer of 1 to 6)

  The present invention also relates to the above lubricating oil composition wherein (C) the alkylphenoxycarboxylic acid is (4-nonylphenoxy) acetic acid.

  Furthermore, the present invention is selected from (E-1) a compound represented by the following general formula (5), (E-2) a thiophosphate ester, and (E-3) an amine salt of an acidic phosphate ester based on the total amount of the composition. It is related with the said lubricating oil composition characterized by containing 0.05-5 mass% of at least 1 type of friction reducing agents.

（式（５）中、Ｒ^８及びＲ^１０は、それぞれ炭素数１〜８のアルキル基であり、Ｒ^９は炭素数１〜１２のアルキレン基である。）

(In formula (5), R ⁸ and R ¹⁰ are each an alkyl group having 1 to 8 carbon atoms, and R ⁹ is an alkylene group having 1 to 12 carbon atoms.)

  According to the present invention, a solvent refined oil having a high aromatic content and sulfur content and a low viscosity index is used as a base oil, and has an oxidation stability equivalent to or better than a highly refined base oil and is inexpensive. A lubricating oil composition is provided.

The present invention will be described below.
As the mineral oil used as the base oil of the lubricating oil composition of the present invention, for example, a lubricating oil fraction obtained by subjecting crude oil to atmospheric distillation and vacuum distillation is subjected to solvent removal, solvent extraction, solvent dewaxing, Paraffinic and naphthenic oils can be used, which are refined by appropriately combining catalytic dewaxing, sulfuric acid washing, purification treatment such as clay treatment, and the like. In addition, hydrocracking and hydrorefining may be combined as necessary, but it is important to minimize the amount from the viewpoint of economy. These base oils may be used alone or in combination of two or more at any ratio.

The total aromatic content of the lubricating base oil is 10 to 50% by mass, preferably 10 to 40% by mass. Moreover, sulfur content is 0.1-1.0 mass%, Preferably it is 0.1-0.8 mass%, More preferably, it is 0.2-0.6 mass%. When the total aromatic content is less than 10% by mass, the cost for purification increases, which is not preferable. When the total aromatic content exceeds 50% by mass, the effect of adding the antioxidant becomes insufficient.
Here, the total aromatic content is “Analytical Chemistry”, Vol. 44, No. 6 (1972), pages 915-919 “Separation of High-Boiling Petroleum Distillates Using Gradient Elution Through Dual-Packed (Silica Gel-Alumina Gel) Adsorption”. It was measured according to the silica-alumina gel chromatographic analysis method described in “Columns”. However, in this method, silica gel is filled in the lower layer, alumina gel is filled in the upper layer, n-heptane is used for elution of saturated hydrocarbon components, benzene is used for elution of aromatic hydrocarbon components, and resin (or polar compound) Each component was fractionated by using methanol for elution, and the aromatic content was measured.

  The viscosity index of the lubricating base oil is 85 to 100, preferably 90 to 100, and more preferably 95 to 100. When the viscosity index is less than 85, the total aromatic content, sulfur content, and nitrogen content increase, which is not preferable, and when it exceeds 100, the purification cost increases, which is not preferable.

  The pour point of the lubricating base oil is −10 ° C. or lower, preferably −15 ° C. or lower, and more preferably −20 ° C. or lower. A pour point higher than −10 ° C. is not preferable for use in winter or cold regions.

No particular limitation is imposed on the viscosity of the lubricating base oil used in the present invention, usually, it is preferable that a viscosity of 10 to 1000 mm ² / s at 40 ° C., and more preferably 20 to 500 mm ² / s.

  In the present invention, the lubricating base oil may be used alone or in combination with other highly refined base oils or synthetic oils, but the content of the lubricating base oil is preferably 50% by mass or more. Preferably it is 70 mass% or more, More preferably, it is 80 mass% or more.

  The antioxidant (B) used in the present invention is not particularly limited, and any antioxidant that is generally used in lubricating oils such as phenolic antioxidants and amine antioxidants can be used. is there.

  Examples of phenolic antioxidants include 4,4′-methylenebis (2,6-di-tert-butylphenol), 4,4′-bis (2,6-di-tert-butylphenol), 4,4 ′. -Bis (2-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), 4,4′-isopropylidenebis (2,6-di-tert-butylphenol), 2,2′-methylenebis (4-methyl-6) -Nonylphenol), 2,2'-isobutylidenebis (4,6-dimethylphenol), 2,2'-methylenebis (4-methyl) 6-cyclohexylphenol), 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4-dimethyl-6-tert-butylphenol, 2, 6-di-tert-α-dimethylamino-p-cresol, 2,6-di-tert-butyl-4 (N, N′-dimethylaminomethylphenol), 4,4′-thiobis (2-methyl-6) -Tert-butylphenol), 4,4'-thiobis (3-methyl-6-tert-butylphenol), 2,2'-thiobis (4-methyl-6-tert-butylphenol), bis (3-methyl-4- Hydroxy-5-tert-butylbenzyl) sulfide, bis (3,5-di-tert-butyl-4-hydroxybenzyl) sulfide 2,2′-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], tridecyl-3- (3,5-di-tert-butyl-4-hydroxy Phenyl) propionate, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) ) Propionate, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 3-methyl-5-tert-butyl-4-hydroxyphenyl substituted fatty acid esters and the like are preferable examples. Can do. These may be used individually by 1 type, or may mix and use 2 or more types.

  Examples of amine-based antioxidants include alkylphenyl-, such as phenyl-α-naphthylamine, p-octylphenyl-α-naphthylamine, p-nonylphenyl-α-naphthylamine, and p-dodecylphenyl-α-naphthylamine. Examples include α-naphthylamines, and dialkyldiphenylamines represented by p, p′-dioctyldiphenylamine, p, p′-dinonyldiphenylamine, p, p′-didodecyldiphenylamine, and the like. These may be used individually by 1 type, or may mix and use 2 or more types.

  Further, the phenolic antioxidant and the amine antioxidant may be used in combination.

  The blending amount of the component (B) in the lubricating oil composition of the present invention is 0.01% by mass, preferably 0.1% by mass, while the upper limit is 5%, based on the total amount of the lubricating oil composition. % By mass, preferably 3% by mass. When the blending amount of the component (B) is less than 0.01% by mass, the effect of improving the oxidation stability due to the blending of the component (B) is not sufficient. On the other hand, when the blending amount exceeds 5% by mass, the blending amount This is not preferable because the effect of improving the oxidative stability sufficient to meet the requirements cannot be obtained and it is economically disadvantageous.

The component (C) used in the present invention is an alkylphenoxycarboxylic acid represented by the following general formula (1).

Formula (1), ^{R 1} represents an alkyl group having 1 to 12 carbon atoms. Specifically, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, and linear and branched pentyl groups, A hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group are shown. Of these, an octyl group, a nonyl group, and a decyl group are preferable.
N represents an integer of 1 to 6, and specifically represents a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, a pentyl group, an isopentyl group, a hexyl group, and an isohexyl group. Of these, a methylene group and an ethylene group are preferable.

  The blending amount of the component (C) in the lubricating oil composition of the present invention is 0.01% by mass, preferably 0.02% by mass, based on the total amount of the lubricating oil composition, while the upper limit is 0. 0.1% by mass, preferably 0.08% by mass. When the blending amount of the component (C) is less than 0.01% by mass, the effect of improving the oxidation stability due to the blending of the component (C) is not sufficient, while when the blending amount exceeds 0.1% by mass, Since the effect of improving the oxidative stability corresponding to the blending amount cannot be obtained and it is economically disadvantageous, it is not preferable.

The component (D) used in the present invention is a triazole derivative. As the triazole derivative, triazole derivatives represented by the following general formulas (2), (3) and (4) are preferable.

In the formula (2), R ² represents a methylene group or an ethylene group from the viewpoint of particularly excellent antioxidant properties, and R ³ and R ⁴ are the same or different groups, and are a hydrogen atom or a carbon number of 1-18. A linear or branched alkyl group, preferably a linear or branched alkyl group having 1 to 12 carbon atoms.

In the formula (3), X ¹ represents a linear or branched alkyl group having 1 to 4 carbon atoms, preferably a methyl group or an ethyl group, and a is 0 to 3, preferably 0, 1 Or the number of 2 is shown and benzotriazole is shown when it is 0. Examples of X ¹ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. As the benzotriazole or alkylbenzotriazole represented by the formula (3), a compound in which X ¹ is a methyl group or an ethyl group, and a is 0, 1 or 2 is particularly excellent in the antioxidant property. Preferable examples include benzotriazole, methylbenzotriazole (tolyltriazole), dimethylbenzotriazole, ethylbenzotriazole, ethylmethylbenzotriazole, diethylbenzotriazole, and mixtures thereof.

In the formula (4), X ² represents a linear or branched alkyl group having 1 to 4 carbon atoms, preferably a methyl group or an ethyl group, R ⁵ represents a methylene group or an ethylene group, and R ⁶ And R ⁷ are the same or different groups, and are a hydrogen atom or a linear or branched alkyl group having 1 to 18 carbon atoms, preferably a linear or branched alkyl group having 1 to 12 carbon atoms. And b is a number from 0 to 3, preferably 0 or 1. Examples of X ² include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. As R ⁶ and R ⁷ , for example, a hydrogen atom, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, straight chain or A branched pentyl group, a linear or branched hexyl group, a linear or branched heptyl group, a linear or branched octyl group, a linear or branched nonyl group, a linear or branched decyl group, Linear or branched undecyl group, linear or branched dodecyl group, linear or branched tridecyl group, linear or branched tetradecyl group, linear or branched pentadecyl group, linear or branched Alkyl groups such as a hexadecyl group, a linear or branched heptadecyl group, and a linear or branched octadecyl group.

As the (alkyl) aminobenzotriazole represented by the above formula (4), X ² is a methyl group, b is 0 or 1, and R ⁵ is a methylene group or the Dialkylaminoalkylbenzotriazole, dialkylaminoalkyltolyltriazole, a mixture thereof, or the like, which is an ethylene group and R ⁶ and R ⁷ are linear or branched alkyl groups having 1 to 12 carbon atoms, are preferably used.

  The blending amount of component (D) in the lubricating oil composition of the present invention is 0.005% by mass, preferably 0.01% by mass, with the upper limit being 0%, based on the total amount of the lubricating oil composition. 0.1% by mass, preferably 0.07% by mass. When the blending amount of the component (D) is less than 0.005% by mass, the effect of improving the oxidation stability due to the blending of the component (D) is not sufficient, while when the blending amount exceeds 0.1% by mass, Since the effect of improving the oxidative stability corresponding to the blending amount cannot be obtained and it is economically disadvantageous, it is not preferable.

  The component (E) used in the present invention is selected from (E-1) a compound represented by the following general formula (5), (E-2) a thiophosphate ester, and (E-3) an amine salt of an acidic phosphate ester. At least one friction reducing agent.

The component (E-1) is a compound represented by the following general formula (5).

In the formula (5), ^{R 8} and ^{R 10} is an alkyl group having 1 to 8 carbon atoms, ^{R 9} is an alkylene group having 1 to 12 carbon atoms. Preferably, R ⁸ and R ¹⁰ are alkyl groups having 1 to 5 carbon atoms, and R ⁹ is an alkylene group having 1 to 4 carbon atoms. Specifically, for example, ethyl-3-[{bis (1-methylethoxy) phosphinothioyl} thio] propionate in which R ⁸ is a 1-methyl-ethyl group, R ¹⁰ is an ethyl group, and R ⁹ is an ethylene group. Is preferably used.

The component (E-2) is a thiophosphate ester, and a thiophosphate ester represented by the following general formula (6) is preferable.

In the formula (6), R ¹¹ is hydrogen or an alkyl group having 1 to 8 carbon atoms, preferably hydrogen or a linear or branched alkyl group having 3 to 6 carbon atoms, all of which may be hydrogen. All may be alkyl groups or a mixture thereof. Further, specifically, for ^{example, R 11} is tert- butyl is a group tri (tert- butylphenyl) thiophosphoric acid ester and ^{R 11} is a mixture of triphenyl thiophosphate ester hydrogen are preferably used.

The component (E-3) is an amine salt of an acidic phosphate ester, and an acidic phosphate ester represented by the following general formula (7) and an alkylamine salt represented by the general formula (8) are preferable.

In the formula (7), R ¹² is a linear or branched alkyl group having 1 to 12 carbon atoms, preferably a linear or branched alkyl group having 4 to 8 carbon atoms, specifically For example, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, linear or branched pentyl group, linear or branched hexyl group, linear or branched heptyl group, straight Examples include alkyl groups such as chain or branched octyl groups. n is 1 or 2.

In the formula (8), R ¹³ and R ¹⁴ are each independently a linear or branched alkyl group having 6 to 18 carbon atoms, preferably each having 8 to 16 carbon atoms. More preferably a linear or branched alkyl group having 11 to 14 carbon atoms, and R ¹³ and R ¹⁴ may be the same or different.

  The blending amount of the component (E) in the lubricating oil composition of the present invention is 0.05% by mass, preferably 0.1% by mass, while the upper limit is 5%, based on the total amount of the lubricating oil composition. % By mass, preferably 3% by mass. When the blending amount of the component (E) is less than 0.05% by mass, the lubricating effect due to the blending of the component (E) is not sufficient. On the other hand, when the blending amount exceeds 5% by mass, it is only commensurate with the blending amount. It is not preferable because the effect of improving lubricity is not obtained and it is economically disadvantageous.

  In the present invention, for the purpose of further improving its performance, if necessary, other antioxidants, rust inhibitors, metal deactivators, antiwear agents, viscosity index improvers, pour point depressants, You may contain various additives represented by an antifoamer, a demulsifier, a stick slip prevention agent, an oiliness agent, etc. individually or in combination of several types.

  The lubricating oil composition of the present invention may be used in combination with a sulfur-based, zinc dithiophosphate-based, phenothiazine-based antioxidant, in addition to a phenol-based antioxidant and an amine-based antioxidant.

Specific examples of the rust inhibitor include partial esters of polyhydric alcohols; esters such as lanolin fatty acid esters, alkyl succinic acid esters, and alkenyl succinic acid esters; sarcosine; polyhydric alcohol partial esters such as sorbitan fatty acid esters; Examples include metal soaps such as fatty acid metal salts, lanolin fatty acid metal salts, and oxidized wax metal salts; sulfonates such as calcium sulfonate and barium sulfonate; oxidized wax; amines; phosphoric acid;
In the present invention, one or two or more compounds arbitrarily selected from these rust inhibitors can be contained in the lubricating oil composition in any amount, but usually the content is The total amount of the lubricating oil composition is preferably 0.01 to 1% by mass.

  The lubricating oil composition of the present invention contains a triazole as an essential component as an antioxidant or a metal deactivator, and examples of other metal deactivators include thiadiazole and imidazole compounds. it can. In the present invention, one kind or two or more kinds of compounds arbitrarily selected from these metal deactivators can be contained in any amount, but the content thereof is usually a lubricating composition. It is desirable that it is 0.001-1 mass% on the basis of the total amount of things.

  Specific examples of the viscosity index improver include a copolymer of one or more monomers selected from various methacrylates or a hydrogenated product thereof, an ethylene-α-olefin copolymer (as α-olefin). Can be exemplified by propylene, 1-butene, 1-pentene, etc.) or a hydride thereof, polyisobutylene or a hydrogenated product thereof, a hydride of a styrene-diene copolymer, and a so-called non-dispersed viscosity. An index improver etc. can be illustrated. In the present invention, one or two or more compounds arbitrarily selected from these viscosity index improvers can be contained in any amount, but the content is usually determined by hydraulic fluid. The content is desirably 0.01 to 10% by mass based on the total amount of the composition.

  Specific examples of the pour point depressant include copolymers of one or more monomers selected from various acrylic esters and methacrylic esters or hydrogenated products thereof, or styrene-diene copolymers. . In the present invention, one kind or two or more kinds of compounds arbitrarily selected from these pour point depressants can be contained in any amount, but the content is usually determined as a lubricating oil composition. It is desirable that it is 0.01-5 mass% on the basis of the total amount of things.

  In addition, specific examples of antifoaming agents include silicones such as dimethyl silicone and fluorosilicone. In the present invention, one or two or more compounds arbitrarily selected from these antifoaming agents can be contained in any amount, but the content is usually the lubricating oil composition. It is desirable that it is 0.001-0.05 mass% on the basis of the total amount. Examples of the demulsifier include polyoxyalkylene glycol, polyoxyalkylene alkyl ether, polyoxyalkylene alkylamide, polyoxyalkylene fatty acid ester and the like. Specific examples of the stick-slip preventing agent include polyhydric alcohol esters (complete esters and partial esters). Specific examples of the oily agent include fatty acids, esters, alcohols and the like. Usually, the content is desirably 0.01 to 0.5% by mass based on the total amount of the lubricating oil composition.

  The lubricating oil composition of the present invention is particularly suitably used as a bearing oil, but in addition, engine oils such as gasoline engine oils and diesel engine oils; automotive gear oils (automatic transmission oils, manual transmission oils, differentials) Oil) and gear oil such as industrial gear oil; hydraulic oil; compressor oil; refrigeration oil; cutting oil, plastic working oil (rolling oil, press oil, forging oil, drawing oil, drawing oil, punching oil, etc.), It is also preferably used in various lubricating oils such as heat treating oils, metal working oils such as electric discharge machining oils, sliding guide surface oils, rust prevention oils, and heat medium oils.

  Hereinafter, the contents of the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Examples 1 to 4 and Comparative Examples 1 to 4]
Table 1 shows the properties of the solvent refined base oil (A1) of the component (A) used in the present invention and the highly hydrorefined base oil (A2) used for comparison.
Lubricating oil compositions according to the present invention were prepared according to the compositions shown in Table 2 (Examples 1 to 4). Moreover, the composition for a comparison was prepared with the composition shown in Table 3 (Comparative Examples 1-4). In addition, the (B)-(E) component used by the Example and the comparative example is as follows.

(B) component B1: 2,6-di-tert-butyl-p-cresol B2: p-dodecylphenyl-α-naphthylamine (C) component C1: (4-nonylphenoxy) acetic acid (D) component D1: N, N-bis (2-ethylhexyl)-[(1,2,4-triazol-1-yl) methyl] amine D2: N, N-bis (2-ethylhexyl)-(4 or 5) -methyl-1H-benzo Triazole-1-methylamine (E) component E1: Ethyl-3-[{bis (1-methylethoxy) phosphinothioyl} thio] propionate E2: Tri (tert-butylphenyl) thiophosphate and triphenylthiophosphate Mixture with ester E3: Salt of hexyl acid phosphate with branched alkyl amine having 11 to 14 carbon atoms

  The oxidation stability of the compositions of these examples and comparative examples was evaluated. The oxidation stability was evaluated by a rotating cylinder type oxidation stability test (RBOT) defined in JIS-K-2514. The results are shown in Table 2 and Table 3.

As is apparent from the results in Table 2, the compositions of the present invention (Examples 1 to 4) exhibit excellent oxidation life characteristics such that the RBOT life exceeds 300 minutes.

On the other hand, when the content of the component (D) as shown in Comparative Example 1 in Table 3 is too small (when the additive component specified in the present invention is insufficient), the base as shown in Comparative Example 2 and Comparative Example 3 is used. When the oil composition is outside the range defined in the present invention, the performance is insufficient.
Further, as shown in Comparative Example 4, even when the content of the component (E) is too large, sufficient oxidation stability cannot be maintained.

Claims (2)

(A) The composition has a total aromatic content of 10 to 50 mass%, a sulfur content of 0.1 to 1.0 mass%, a viscosity index of 85 to 100, and a pour point of -10 ° C or lower. A base oil containing 50% by mass or more of the mineral oil, based on the total amount of the composition, (B) 0.01 to 5% by mass of the antioxidant, (C) an alkylphenoxycarboxylic acid represented by the following general formula (1) 0.01-0.1% by mass, and (D) 0.005-0.1% by mass of a triazole derivative represented by the following general formula (2), and (E-1) in the following general formula (5) 0.05 to 5% by mass of a friction reducing agent comprising a compound of (E-2) thiophosphate, (E-3) hexyl acid phosphate and a branched alkyl amine having 11 to 14 carbon atoms A lubricating oil composition characterized by comprising.

(In formula (1), R ¹ represents an alkyl group having 1 to 12 carbon atoms, and n represents an integer of 1 to 6)

(In the formula (2), R ² represents a methylene group or an ethylene group, R ³ and R ⁴ are the same or different groups, and are a hydrogen atom or a linear or branched alkyl having 1 to 18 carbon atoms. Group.)

(In formula (5), R ⁸ and R ¹⁰ are each an alkyl group having 1 to 8 carbon atoms, and R ⁹ is an alkylene group having 1 to 12 carbon atoms.) The lubricating oil composition according to claim 1, wherein the (C) alkylphenoxycarboxylic acid is (4-nonylphenoxy) acetic acid.